Sunday, February 20, 2011

Measuring, Marking Out, and (tentatively) Cutting

The job I seem to spend most of my time doing these days is measuring and marking timber for cutting or drilling. This is only partly a complaint. Accurate measuring is important and I enjoy doing it but I also enjoy doing more noticeable work, like drilling holes or making iron-ware.

I'd had a week off from the railway to go to my nephew's birthday party in London so I arrived there yesterday, Saturday 19th February, to find that the short longitudinals and diagonals had be cut to accomodate the draw-bar transverse springs. Before we can assemble them and the headstocks we have to drill through them so that the upper and lower parts can be bolted together round the springs.

My first job was to fit the diagonals and mark out the position of the oblique holes that are to accommodate the 1" tie-bars between the headstock and the transverse beams.

The tie-bar goes through the diagonal at an oblique angle as shown buy the red line. We decided to try to drill the hole ourselves. I marked the line of the hole along the top edge of the diagonal and projected the centre and edges down the face of the beam. I then marked the position of the centre of the hole down from the top of the beam. Ollie used a small diameter twist bit to drill a pilot hole to guide the flat-bit that we would use to make the hole. I then cut a wedge out of the beam face deep enough at the centre-line of the hole so that the full radius of the flat-bit would make contact with the face of the timber. We began drilling. It went well for a while but coming in at such an oblique angle meant that we had to put a long extension on the drill-bit. Keeping the drill perpendicular to the lines was difficult and in the end as I withdrew the rotating bit from the hole it snagged and bent the shaft as well as doing some damage to the timber.

We decided that it would be better if Mark, the carpenter who made the frames and who has better tools at his disposal would drill the holes. So Ollie called him and asked him to do just that.

So now we have a pile of timbers marked up ready for Mark to drill the diagonals and for Ollie to drill the holes for the 5/8" bolts that will hold the diagonals and short-longitudinals together.

I had a moment of realisation as I looked at the diagonals and longitudinals. I understood at last why they are jointed into the headstocks and cross-beams as they are. With the whole frame completed it will be possible to drop out the bottoms of the diagonals and short-longitudinals and raise the transverse-springs into place before putting the diagonals and longitudinals back together to hold the springs in place. I had thought we'd have to insert the springs before we finished assembling the frame!


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